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Katrin FAESSLER

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Analytic characterization of QC maps on H 1<br />

Theorem (Korányi, Reimann, Pansu, Vodop’yanov)<br />

A homeomorphism f : Ω → Ω ′ between domains in H 1 is quasiconformal if<br />

and only if<br />

f ∈ HW 1,4<br />

loc (Ω),<br />

f is a weakly contact map,<br />

Here,<br />

∃ 1 ≤ K < ∞ such that DHf (p) 4 ≤ KJ(p, f ) a.e.<br />

DHf 4 = (|ZfI | + |¯ZfI |) 4<br />

and J(·, f ) = (|ZfI | 2 − |¯ZfI | 2 ) 2 .<br />

Definition (Distortion)<br />

<br />

<br />

|ZfI<br />

K(·, f ) = <br />

| + |ZfI | <br />

<br />

<br />

|ZfI | − |ZfI |<br />

and Kf = K(·, f )∞.<br />

Note: H(·, f ) = K(·, f ) a.e.<br />

<strong>Katrin</strong> Fässler (University of Helsinki) A stretch map on H 1<br />

HCAA 2012 13 / 23

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